* Sexual desire and orgasm are subject to various influences on the brain and nervous system, which controls the sex glands and genitals.

* The ingredients of desire may differ for men and women, but researchers have revealed some surprising similarities. For example, visual stimuli spur sexual stirrings in women, as they do in men.

* Achieving orgasm, brain imaging studies show, involves more than heightened arousal. It requires a release of inhibitions engineered by shutdown of the brain’s center of vigilance in both sexes and a widespread neural power failure in females.